window.onload = function() {
	var play = document.getElementById("play");
	var title = document.getElementById("title");
	title.style.display = "none";
	//鼠标事件
	play.onclick = function(event) {

			title.style.display = "block";
			if (event.stopPropagation) {
				event.stopPropagation();
			} else {
				event.cancelBubble = true;
			}
			alert("you click  this button!");
		}
		// 点击页面空白处时
	document.onclick = function(event) {
		title.style.display = "none";
		alert("you click  blank!");
	}
}